(1) Field of the Invention
The present invention relates to a structure of a flexible tube of an endoscope which is used in the medical and industrial fields. More particularly, the present invention relates to a technique, according to which a shape memory alloy is built in a flexible tube and the flexible tube is inserted into a complicatedly bent portion while straightening the bent portion by utilizing the restoring property of the shape memory alloy according to need.
(2) Description of the Prior Art
When the interior of the colon is observed by using an endoscope having a long flexible tube, such as a colon endoscope, it is very difficult to insert a flexible tube 10 into the complicately bent, long colon, as shown in FIG. 1-(I), because the tube 10 can hardly be advanced in the bent portion. Accordingly, there is ordinarily adopted a method in which, as shown in FIG. 1-(III), a stylet 12 composed of an elastic material such as a piano wire is inserted into or withadrawn from the flexible tube 10 to straighten the bent portion of the colon and the flexible tube is thus inserted little by little. However, when the stylet 12 is going to be inserted into the bent portion of the flexible tube 10 as shown in FIG. 1-(II), the stylet 12 merely presses the bent portion of the flexible tube 10 but the stylet 12 cannot be inserted into the flexible tube 10, with the result that the flexible tube cannot be straightened. If it is intended to forcibly insert the stylet 12 into the flexible tube 10, there arises a risk of breakage of the flexible tube 10. However, if the stylet 12 is not inserted into the bent portion, the bent portion cannot be straightened. Accordingly, the conventional method is technically contradictory, and the observation of the colon or the like with an endoscope involves serious difficulties.
It may be considered that good results will be obtained if the stylet is inserted into the flexible tube in advance and the flexible tube is inserted into the bent portion. However, in this case, the flexibility is lost in the stylet-inserted flexible tube and insertion of the flexible tube into the bent portion becomes impossible.
Accordingly, the success in the observation of the colon or the like with an endoscope has heretofore depended on the skill and experience of an operator.